Electro-optic element and scanning optical device

ABSTRACT

An electro-optic element includes an electro-optic crystal having a birefringent property, and in which a refractive index distribution is generated in accordance with an intensity of an electric field caused inside, a pair of intensity modulating electrodes for applying a voltage for varying the birefringent property of the electro-optic crystal, a pair of scanning electrodes for applying a voltage for varying the refractive index distribution of the electro-optic crystal, and a polarization selection member provided at least on a side of a laser beam emission end face out of a laser beam entrance end face and the laser beam emission end face of the electro-optic crystal, and for selectively transmitting a part with a specific vibration direction out of a light beam emitted from the electro-optic crystal.

This is a Continuation of application Ser. No. 12/036,811 filed Feb. 25,2008. The disclosure of the prior application[s] is hereby incorporatedby reference herein in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to an electro-optic element and a scanningoptical device.

2. Related Art

In recent years, a scanning image display device for displaying an imageby raster-scanning a light beam such as a laser beam on an irradiatedsurface has been proposed. In this device, high contrast display ispossible in comparison with a projector or the like using, for example,a liquid crystal light valve because complete black color can bedisplayed by stopping supply of the laser beam. Further, since an imagedisplay device using a laser beam has characteristics such that thesingle-wavelength laser beam causes high color purity, and that the highcoherence thereof makes the shaping (aperturing) of the beam easy, theimage display device using the laser beam is expected to be ahigh-quality display achieving a high resolution and high colorreproducibility. Further, since the scanning image display device doesnot have any fixed pixels unlike with a liquid crystal display, a plasmadisplay, and so on, the scanning image display device does not have aconcept of the number of pixels, and consequently, has an advantage thatthe resolution can easily be converted.

In order for generating an image by the scanning image display device,it is necessary to scan a light beam two-dimensionally using a scannersuch as a polygon mirror or a galvanometer mirror. Although a method ofscanning the light beam two-dimensionally by swinging a single scannerin two directions, namely a horizontal direction and a verticaldirection can be considered, in such a case, there arises a problem thatthe structure and control of the scanning system become complicated.Therefore, there has been proposed a scanning image display deviceprovided with two sets of scanners each for scanning a light beamone-dimensionally and arranged to have charges of horizontal scanningand vertical scanning, respectively. In the past, it has been common touse polygon mirrors or galvanometer mirrors for both of the scanners,and a projection device using rotating polygon mirrors for both of thescanners is disclosed in JP-A-1-245780.

However, although in the above document the device using the polygonmirrors is introduced, the scanning frequency increases with increase inresolution of the image format, and approaches the limit with polygonmirrors or galvanometer mirrors. Therefore, in recent years, a systemapplying the microelectromechanical systems (MEMS) technology to thehigher-speed scanner has been introduced. A scanner (hereinafter simplyreferred to as a MEMS scanner) applying the MEMS technology denotes ascanner manufactured using a fine processing technology of asemiconductor material such as silicon, in which a mirror supported by atorsion spring and so on is driven with electrostatic force. Thisscanner can scan a light beam by reciprocating the mirror with theinteraction of the electrostatic force and the restoring force of thespring. By using the MEMS scanner, a high-frequency scanner with a largedeflection angle in comparison with past scanners can be realized. Thus,it becomes possible to display a high-resolution image.

Incidentally, since the reciprocating motion of the mirror at theresonance frequency is required for realizing a high-speed MEMS scanner,in consideration of efficiency of a light beam, there is adopted asystem in which a scanning line is formed from left to right viewed fromthe viewer, and then the next scanning line is formed from right to left(bi-directional scanning).

On the other hand, since the image signal is standardized based oncathode ray tubes (CRT), the format thereof corresponds to scanning(unidirectional scanning) in which the scanning point moves from left toright, then returns to left in a short period of time, and moves toright again. Therefore, in the case with the MEMS scanner, regarding apart of the data, the order of the signals needs to be reversed whendisplaying the data, and consequently, the control of the signalsbecomes complicated.

Consequently, as a scanning method other than the MEMS scanner, therecan be cited an electro-optic (EO) scanner. The EO scanner is an elementin which the proceeding direction of a light beam transmitted through anEO crystal is changed by applying a voltage to the EO crystal. Asdescribed above, since in the EO scanner the scanning angle can becontrolled by the voltage, drawing with the unidirectional scanningbecomes possible similarly to the CRT.

Further, in the EO scanner, electrons are injected in the EO crystal byapplying the voltage thereto, thus unevenness is generated in theelectron distribution. Therefore, the distribution is generated in therefractive index alteration caused by a Kerr effect to deflect theincident light beam towards the side with a higher refractive index,thus making the scanning of the light beam possible. Further, since thegradient of the refractive index distribution inside the EO crystaldepends on the amount of the injected electrons, namely the appliedvoltage, by varying the applied voltage, the scanning angle of the lightbeam emitted from the EO crystal can be controlled.

Incidentally, in a display device using the EO scanner, it is necessaryto modulate the intensity at positions corresponding to respectivepixels in order for displaying the image. In the case in which SuperVideo Graphics Array (SVGA) class display is performed, the modulationrate higher than about 30 MHz is necessary. However, depending on thetype of the laser source, there arises a problem that the sufficientmodulation rate can hardly be obtained. Further, although it is alsopossible to provide an external modulator using an electro-optic elementor an acousto-optic element separately from the EO scanner, there arisesa problem that increase in the number of elements incurs rise in cost,and further, requires an additional volume resulting in growth in size.

SUMMARY

An advantage of some aspects of the present invention is to provide anelectro-optic element and a scanning optical device which are eachhigh-speed and capable of obtaining a large deflection angle, and at thetime, compact and moderate in cost.

In order for obtaining the above advantage, the invention provides thefollowing measures.

An electro-optic element according to an aspect of the inventionincludes an electro-optic crystal having a birefringent property, and inwhich a refractive index distribution is generated in accordance with anintensity of an electric field caused inside, a pair of intensitymodulating electrodes for applying a voltage for varying thebirefringent property of the electro-optic crystal, a pair of scanningelectrodes for applying a voltage for varying the refractive indexdistribution of the electro-optic crystal, and a polarization selectionmember provided at least on a side of a laser beam emission end face outof a laser beam entrance end face and the laser beam emission end faceof the electro-optic crystal, and for selectively transmitting a partwith a specific vibration direction out of a light beam emitted from theelectro-optic crystal.

In the electro-optic element according to an aspect of the invention,voltages are applied to the intensity modulating electrodes and thescanning electrodes. Thus, since the birefringent property is caused inan area of the electro-optic crystal to which the voltage is applied bythe intensity modulating electrodes, the light beam entering this areais rotated in the polarization plane in accordance with the value of thevoltage applied thereto. Further, in an area of the electro-opticcrystal to which the voltage is applied by the scanning electrodes, therefractive index distribution of the electro-optic crystal increases ordecreases continuously along one direction in accordance with theelectric field caused inside. Therefore, the laser beam proceeding in adirection perpendicular to the electric field caused inside theelectro-optic crystal is deflected from the side with a low refractiveindex towards the side with a high refractive index. Further, a partwith the specific vibration direction of the light beam emitted from theelectro-optic crystal is transmitted by the polarization selectionmember provided to the emission end face of the electro-optic crystal,in accordance with the polarization plane thereof. As described above,the light beam entering the electro-optic crystal is modulated and thenemitted.

Therefore, by providing the intensity modulating electrodes and thescanning electrodes to the electro-optic crystal, it becomes possible tomodulate the intensity of the incident light beam and to scan theincident light beam with a single electro-optic crystal. Therefore, evenin the case in which a light beam emitted from a light source devicewhich cannot provide sufficient modulation rate of the light beam suchas a light source with a wavelength conversion element is input, itbecomes possible to increase the modulation rate by controlling thevoltage applied to the intensity modulating electrodes of theelectro-optic crystal.

Specifically, the modulation equivalent to an external modulator usingan acousto-optic element becomes possible, and it becomes possible toobtain the high speed electro-optic element with a large deflectionangle. Further, since the modulation rate is raised using theelectro-optic crystal for scanning the light beam as an additional usageinstead of raising the modulation rate using a separate optical member,it becomes possible to provide the compact electro-optic element withmoderate cost.

Further, in the electro-optic element according to this aspect of theinvention, it is preferable that the electro-optic crystal is composedof a modulating area held between the intensity modulating electrodesand a scanning area held between the scanning electrodes sequentiallydisposed from the laser beam entrance end face along a proceedingdirection of the laser beam.

In the electro-optic element according to this aspect of the invention,the light beam input from the entrance end face of the electro-opticcrystal is firstly modulated in the modulating area. Then, the modulatedlight beam is input to the scanning area, and is scanned. On thisoccasion, the light beam entering the scanning area is input in adirection perpendicular to the entrance end face of the scanning area.In contrast to this aspect of the invention, if the scanning area andthe modulating area are sequentially disposed, since the light beamemitted from the scanning area is input to the modulating area from anoblique direction, there arises a concern that the light beam proceedingin the modulating area is not rotated to have the predeterminedpolarization plane. Therefore, by providing the modulating area and thescanning area in this order as in this aspect of the invention, itbecomes possible to more accurately scan and modulate the light beamentering the electro-optic crystal.

Further, in the electro-optic element according to this aspect of theinvention, it is preferable that the intensity modulating electrodes andthe scanning electrodes are different in material from each other.

In the electro-optic element according to this aspect of the invention,since the intensity modulating electrodes and the scanning electrodesare different in material from each other, the both characteristics ofthe birefringent property and the refractive index distribution cansurely be brought out in the electro-optic crystal. Therefore, both ofthe intensity modulation and the deflection of the light beam enteringthe electro-optic crystal can surely be performed.

Further, in the electro-optic element according to this aspect of theinvention, it is preferable that the electro-optic crystal includes acomponent of KTa_(1-x)Nb_(x)O₃.

In the electro-optic element according to this aspect of the invention,the electro-optic crystal is a crystal (hereinafter referred to as a KTNcrystal) having a component of KTa_(1-x)Nb_(x)O₃ (potassium tantalateniobate), which is a dielectric material with a high permittivity. TheKTN crystal has a property of changing the crystal system from a cubicalcrystal to a tetragonal crystal, and further to a rhombohedral inaccordance to the temperature, and it is known that it has a largesecond-order electro-optic effect in the cubical crystal. In particular,in an area close to the phase transition temperature from the cubicalcrystal to the tetragonal crystal, there occurs a phenomenon that therelative permittivity diverges, and the second-order electro-opticeffect proportional to the square of the relative permittivity becomesan extremely large value. Therefore, the crystal with the component ofKTa_(1-x)Nb_(x)O₃ can suppress the applied voltage necessary for varyingthe refractive index to a lower value compared to other crystals. Thus,the electro-optic element capable of achieving low power consumption canbe provided.

A scanning optical device according to another aspect of the inventionincludes a light source device for emitting a laser beam, and theelectro-optic element described above for modulating the laser beamemitted from the light source device in accordance with an image signal,and scanning the laser beam towards an irradiated surface.

In the scanning optical device according to this aspect of theinvention, the laser beam emitted from the light source device ismodulated in accordance with the image signal, and scanned towards theirradiated surface by the electro-optic element. On this occasion, asdescribed above, by using the electro-optic element capable ofperforming the intensity modulation, and having a large deflectionangle, a scanning optical device using a scanning device capable ofaccepting high resolution can be obtained. Therefore, the scanningoptical device capable of achieving downsizing of the whole device, anddisplaying an image more clearly on the irradiated surface withoutcausing deterioration of the image quality can be obtained.

Further, in the scanning optical device according to this aspect of theinvention, it is preferable that the light source device emits aplurality of laser beams with wavelengths different from each other, andthe polarization selection member selectively transmits a part with aspecific vibration direction out of the laser beam in a specificwavelength range out of wavelength ranges of the plurality of laserbeams, and transmits the laser beams outside the specific wavelengthrange irrespective of vibration directions.

In the scanning optical device according to this aspect of theinvention, as the polarization selection member, for example, whatfunctions on the wavelength range of the light beam having a lowmodulation rate is used. As described above, since the polarizationselection member functions on the wavelength range of the light beamhaving a low modulation rate, when the laser beam emitted from theelectro-optic crystal is transmitted through the polarization selectionmember, only the light beam with low modulation rate should bemodulated. Therefore, since the modulation rates of a plurality of laserbeams with different wavelengths can be adjusted to be the same, itbecomes possible to project a clear image on the irradiated surface.

Further, in the scanning optical device according to this aspect of theinvention, it is preferable that the light source device emits aplurality of laser beams with wavelengths different from each other, theplurality of laser beams is respectively input to different areas of theelectro-optic crystal, and the pair of intensity modulating electrodesis separately provided to each of the different areas.

In the scanning optical device according to this aspect of theinvention, the laser beams with different wavelengths emitted from thelight source device are respectively input to the different areas of theelectro-optic crystal. Further, since the intensity modulatingelectrodes are separately provided to each of the different areas, itbecomes possible to vary the amount of modulation for every laser beamby controlling the voltages applied to the respective intensitymodulating electrodes. Therefore, even in the case in which all of themodulation rates of the plurality of laser beams are insufficient forperforming an appropriate display, high speed modulations necessary forappropriate display and different from each other can be respectivelyexecuted on the plurality of laser beams. Therefore, it becomes possibleto project a clear image on the irradiated surface.

Further, in the scanning optical device according to this aspect of theinvention, it is preferable that the light source device emits aplurality of laser beams with wavelengths different from each other, andthere is provided a control section for controlling driving of the lightsource device so that the plurality of laser beams is scanned in a timesequential manner in a drawing period for one frame.

Further, in the scanning optical device according to this aspect of theinvention, it is preferable that the light source device emits aplurality of laser beams with wavelengths different from each other, andthere is provided a control section for controlling driving of the lightsource device so that the plurality of laser beams is scanned in a timesequential manner in a drawing period for one line.

In the scanning optical device according to this aspect of theinvention, since the laser beams with different wavelengths can bescanned sequentially by one frame or by one line by the control sectioncontrolling driving of the light source device, the laser beams withdifferent wavelengths can be input to the same area of the electro-opticcrystal. Therefore, since the intensity modulating electrodes providedfor each of the laser beams with different wavelengths are not required,downsizing and moderate manufacturing cost can be achieved.

Further, in the case in which the laser beams with different wavelengthsare scanned every frame, each laser beam is irradiated for a longerperiod of time compared to the case of scanning the laser beams everyline, the driving control of the light source devices by the controlsection becomes simple. Further, since the color shift caused by adrawing method does not occur, a clear image can be projected on theirradiated surface.

Further, in the case in which the laser beams with different wavelengthsare scanned every line, the repeating frequency of the color becomeshigher compared to the case of scanning the laser beams with differentwavelengths every frame, thus occurrence of the color break-up can besuppressed. Further, since the driving speed of the slower scanningdevice, namely the vertical scanning rate of the irradiated surface, canbe lowered compared to the case of scanning the laser beams withdifferent wavelengths every frame, the slow scanning device can also beadopted, thus cost reduction is possible.

Further, in the scanning optical device according to this aspect of theinvention, it is preferable that the electro-optic element performshorizontal scanning.

In the scanning optical device according to this aspect of theinvention, the electro-optic element performs the horizontal scanning,and an inexpensive polygon mirror, for example, is used as the verticalscanner, thus an inexpensive and high performance scanning opticaldevice can be realized.

It should be noted that “horizontal scanning” here denotes a fasterscanning out of two directional scanning, and “vertical scanning”denotes a slower scanning.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanyingdrawings, wherein like numbers refer to like elements.

FIG. 1 is a cross-sectional view showing a substantial part of anelectro-optic element according to a first embodiment of the invention.

FIG. 2 is a diagram showing a voltage signal applied to intensitymodulating electrodes shown in FIG. 1.

FIG. 3 is a diagram showing a voltage signal applied to scanningelectrodes shown in FIG. 1.

FIG. 4 is a perspective view showing a modified example of theelectro-optic element according to the first embodiment of theinvention.

FIG. 5 is a perspective view showing a scanning optical device accordingto a second embodiment of the invention.

FIG. 6 is a perspective view showing a scanning optical device accordingto a third embodiment of the invention.

FIG. 7 is a perspective view showing an electro-optic element shown inFIG. 6.

FIG. 8 is a cross-sectional view showing a substantial part of theelectro-optic element shown in FIG. 6.

FIG. 9 is a schematic diagram showing a laser beam projected to anirradiated surface of the scanning optical device according to the thirdembodiment of the invention.

FIG. 10 is a perspective view showing a scanning optical deviceaccording to a fourth embodiment of the invention.

FIG. 11 is a timing chart of driving of a light source device and avoltage applied to an electro-optic element in the scanning opticaldevice according to the fourth embodiment of the invention.

FIG. 12 is a timing chart of driving of a light source device and avoltage applied to an electro-optic element in the scanning opticaldevice according to a fifth embodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, some embodiments of an electro-optic element and a scanningoptical device according to the invention will be explained withreference to the accompanying drawings. It should be noted that thescale size of each member is accordingly altered so that the member isshown large enough to be recognized in the drawings below.

First Embodiment

An electro-optic element 1 has both functions of modulating an incidentlight beam with a birefringent property, and of scanning a laser beamproceeding through the inside thereof by varying the refractive indexdistribution in accordance with the intensity of the electric fieldcaused in the inside thereof. Specifically, as shown in FIG. 1, theelectro-optic element 1 is provided with a pair of intensity modulatingelectrodes 11 a, 11 b, a pair of scanning electrodes 12 a, 12 b, and anoptical element (an electro-optic crystal) 13. Further, the intensitymodulating electrodes 11 a, 11 b are disposed across the optical element13 from each other. Similarly, the scanning electrodes 12 a, 12 b arealso disposed across the optical element 13 from each other.

Further, the laser beam vibrating in an arranging direction of theintensity modulating electrodes 11 a, 11 b as illustrated by the arrow Ain FIG. 1 enters the electro-optic element 1.

The optical element 13 is a dielectric crystal (an electro-opticcrystal) having an electro-optic effect, and is made of a crystallinematerial including a composition of KTN (KTa_(1-x)Nb_(x)O₃, potassiumtantalate niobate) in the present embodiment. Further, the opticalelement 13 has a cuboid shape, and is provided with a polarization plate(a polarization selection member) 15 so as to have contact with anemission end face 13 b thereof opposite to an entrance end face 13 athereof.

The polarization plate 15 is made of inorganic materials, and is a wiregrid polarization plate with wires (thin wires) made of metal such asaluminum formed as stripes on a substrate such as glass. Further, thepolarization plate 15 has a configuration for transmitting a polarizedlight beam with a polarization direction substantially perpendicular tothe extending direction of the wires while reflecting a polarized lightbeam with a polarization direction substantially perpendicular to theabove polarization direction.

Further, the polarization direction (transmission axis) of thepolarization plate 15 is arranged to be a direction (a specificvibration direction) perpendicular to the polarization direction of anincident laser beam. Thus, a black display is performed in the state inwhich no voltage is applied between the intensity modulating electrodes11 a, 11 b (normally black display).

Further, as shown in FIG. 1, the intensity modulating electrodes 11 a,11 b are respectively disposed on one surface 13 c and the other surface13 d opposite to the one surface 13 c of the optical element 13.Further, the scanning electrodes 12 a, 12 b are also disposedrespectively on the one surface 13 c and the other surface 13 d of theoptical element 13, similarly to the intensity modulating electrodes 11a, 11 b.

Each of the intensity modulating electrode 11 a and the scanningelectrode 12 a on the one surface 13 c of the optical element 13 isdisposed in an area obtained by dividing the one surface 13 c into twosubstantially equal parts. Similarly, each of the intensity modulatingelectrode 11 b and the scanning electrode 12 b on the other surface 13 dof the optical element 13 is disposed in an area obtained by dividingthe other surface 13 d into two substantially equal parts.

Further, the intensity modulating electrode 11 a and the scanningelectrode 12 a disposed on the one surface 13 c of the optical element13 are arranged adjacent to each other with a predetermined distancetowards the proceeding direction of the laser beam. Specifically, theintensity modulating electrode 11 a is disposed on the side of theentrance end face 13 a of the one surface 13 c of the optical element13, and the scanning electrode 12 a is disposed on the side of theemission end face 13 b of the one surface 13 c.

Further, also on the other surface 13 d of the optical element 13,similar to the one surface 13 c, there are disposed the intensitymodulating electrode 11 b on the side of the entrance end face 13 a ofthe optical element 13, and the scanning electrode 12 b on the side ofthe emission end face 13 b thereof.

Thus, the optical element 13 has a configuration in which a modulatingarea T1, namely the area held between the intensity modulatingelectrodes 11 a, 11 b, and a scanning area T2, namely the area heldbetween the scanning electrodes 12 a, 12 b, are disposed in sequence.

Firstly, the intensity modulating electrodes 11 a, 11 b will beexplained.

As a material of the intensity modulating electrodes 11 a, 11 b, amaterial inducing a Kerr effect inside the optical element 13 isselected. In the present embodiment, as the electrode material of theintensity modulating electrodes 11 a, 11 b, an electrode material with alarge Schottky barrier such as Pt is used. It should be noted that Pt isnothing more than an example.

Further, a power supply E1 is connected to the intensity modulatingelectrodes 11 a, 11 b for applying a voltage therebetween. Further, theintensity modulating electrodes 11 a, 11 b have the same dimensions inthe proceeding direction of the laser beam L proceeding inside theoptical element 13.

Then, the scanning electrodes 12 a, 12 b will be explained.

As a material of the scanning electrodes 12 a, 12 b, a material forinducing, inside the optical element 13, an effect (a space chargecontrol mode electro-optic effect) that the refractive indexdistribution is controlled by a space charge as shown in FIG. 1 isselected. In the present embodiment, as the electrode material for thescanning electrodes 12 a, 12 b, Ti with which an electric current iseasily injected in the optical element 13 is used. It should be notedthat the electrode material of the scanning electrodes 12 a, 12 b is notlimited to Ti, but can be any materials capable of having an ohmiccontact with the optical element 13 and exerting an effect of reducingthe Schottky barrier.

Further, a power supply E2 is connected to the scanning electrodes 12 a,12 b for applying a voltage therebetween. Further, the scanningelectrodes 12 a, 12 b have the same dimensions in the proceedingdirection of the laser beam L proceeding inside the optical element 13.As described above, it is arranged that voltages can be appliedindependently to the intensity modulating electrodes 11 a, 11 b and thescanning electrodes 12 a, 12 b by the power supplies E1, E2.

Then, the light beam entering the modulating area T1 will be explained.

Since a voltage is applied to the modulating area T1 by the electrodematerial Pt with a large Schottky barrier, the laser beam entering thearea is dominantly influenced by the Kerr effect. Thus, the plane ofpolarization is rotated in accordance with the voltage value appliedbetween the intensity modulating electrodes 11 a, 11 b.

Specifically, such a pulse signal with a voltage value corresponding tothe light intensity as shown in FIG. 2 is applied between the intensitymodulating electrodes 11 a, 11 b by the power supply E1. Thus, the laserbeam entering the modulating area T1 enters an entrance end face T2 a ofthe scanning area T2 with the polarization plane rotated in accordancewith the voltage value of the pulse signal. The laser beam entering thescanning area T2 is emitted from the polarization plate 15 provided tothe emission end face 13 b of the optical element 13 with thepolarization plane maintained in the scanning area T2. On this occasion,the component of the incident light beam different from the transmissionaxis of the polarization plate 15 is reflected by the polarization plate15 while the light beam with the same component as the transmission axisis transmitted through the polarization plate 15 and emitted therefrom.In this way, the intensity modulation of the light beam entering theoptical element 13 is performed.

Then, the light beam entering the scanning area T2 will be explained.

The incident laser beam to the scanning area T2 is dominantly influencedby the space charge control mode electro-optic effect, and consequently,refracted in accordance with the intensity of the electric fieldgenerated in the scanning area T2 in accordance with the value of thevoltage applied between the scanning electrodes 12 a, 12 b.

Such a voltage with a saw-tooth waveform as shown in FIG. 3 is appliedbetween the scanning electrodes 12 a, 12 b by the power supply E2. Itshould be noted that the voltage of the scanning electrode 12 b is fixedto 0V.

When the voltage with an initial value S1 to be applied to the scanningelectrode 12 a is applied to the scanning electrode 12 a, the laser beamL1 proceeding inside the optical element 13 proceeds straight as shownin FIG. 1. Further, when the voltage value to be applied to the scanningelectrode 12 a is gradually raised as illustrated as the voltagewaveform shown in FIG. 3, the refractive index gradient of the opticalelement increases, and the laser beam is emitted with a deflection anglecorresponding to the voltage value. Further, when the maximum voltagevalue S2 is applied to the scanning electrode 12 a, the laser beam L2proceeding in the optical element 13 is significantly deflected in theoptical element 13 and emitted therefrom as shown in FIG. 1.

As described above, it is arranged that by applying the voltage with thewaveform shown in FIG. 3 to the scanning electrode 12 a, the laser beamL emitted from the modulating area T1 is scanned in the scanning rangefrom the laser beam L1 to the laser beam L2 by the scanning area T2 asshown in FIG. 1. Specifically, the light beam entering from the entranceend face 13 a of the optical element 13 proceeds straight in themodulating area T1 with the polarization plane rotated to apredetermined polarization plane, then enters the scanning area T2, andis deflected towards the scanning electrode 12 b. Then, the laser beamdeflected in the scanning area T2 is transmitted through thepolarization plate 15 in accordance with the polarization plane, andthen emitted therefrom.

Further, since in the present embodiment, the laser beam is scanned onlyin one direction, the laser beam is input from the entrance end face 13a of the optical element 13 on the side of the one surface 13 c as shownin FIG. 1. In other words, since in the present embodiment, the laserbeam entering the optical element 13 is deflected towards the othersurface 13 d by the refractive index distribution of the optical element13, by inputting the laser beam on the side of the one surface 13 c ofthe optical element 13, a wide scanning range can be obtained.

According to the electro-optic element 1 according to the presentembodiment, by providing the intensity modulating electrodes 11 a, 11 band the scanning electrodes 12 a, 12 b to the optical element 13, itbecomes possible to modulate the intensity of the incident laser beamand to scan the incident laser beam with a single optical element 13.Therefore, even if a light beam emitted from a light source, whichcannot achieve a sufficient modulation rate of the light beam, is input,the modulation rate can be increased by controlling the voltage appliedto the intensity modulating electrodes 11 a, 11 b of the optical element13.

Specifically, the modulation (several hundreds of megahertz or more)equivalent to an external modulator using an acousto-optic element ispossible, and it becomes possible to obtain the high speed electro-opticelement 1 with a large deflection angle. Further, since the modulationrate is raised using the optical element 13 for scanning the light beaminstead of raising the modulation rate using a separate optical member,it becomes possible to provide the compact electro-optic element 1 withmoderate cost.

In other words, the electro-optic element 1 according to the presentembodiment can obtain a large deflection angle at high speed, and alsocan be made compact with moderate cost.

Further, since the wire grid polarization plate is used as thepolarization plate 15, a polarization-changing optical element vastlysuperior in heat resistance to dielectric multilayer films and hardlycausing light absorption can be obtained. Specifically, since theincident angle dependency of the light beam entering the polarizationsplitting surface can be reduced, the light beam can be transmitted orreflected by the reflective surface without decreasing the amount oflight emitted from the light source, thus the efficiency of light can beimproved.

Further, although the optical element 13 is arranged to have aconfiguration of having the modulating area T1 and the scanning area T2disposed in sequence from the entrance end face 13 a along theproceeding direction of the laser beam, the optical element having thescanning area T2 and the modulating area T1 disposed in this order canalso be adopted.

However, since in the present embodiment, the incident light beam isrotated to have a predetermined polarization plane in the modulatingarea T1, and then scanned in the scanning area T2, it becomes possibleto input the laser beam from a direction perpendicular to the entranceend face T2 a of the scanning area T2. Thus, the incident light beam tothe optical element 13 can more accurately be modulated compared to thecase (the case with the order of scanning area T2 and then themodulating area T1) in which the laser beam enters from an obliquedirection with respect to the entrance end face T1 a of the modulatingarea T1.

Further, in the case of using the external modulator, an alignmentbetween the external modulator and the scanning device providedseparately is necessary. In contrast, in the electro-optic element 1 ofthe present embodiment, such an alignment is not required, andconsequently, the assembly thereof becomes easy.

Further, since the black display is performed in the state in which novoltage is applied between the intensity modulating electrodes 11 a, 11b (normally black display), even if a laser beam is continuously inputto the electro-optic element 1 by chance in the state in which novoltage is applied to the electro-optic element 1, it becomes possibleto surely prevent the light beam from being emitted to the outside fromthe electro-optic element 1.

It should be noted that although the configuration of disposing thepolarization plate 15 so as to have contact with the emission end face13 b of the optical element 13 is adopted, it is also possible todispose the polarization plate 15 at a position distant therefrom andwhere the light beam emitted from the emission end face 13 b can enterthe polarization plate 15.

Further, although in the case in which the light beam to be input to theelectro-optic element 1 has a predetermined polarization direction, thepolarization plate 15 does not need to be used with the entrance endface 13 a of the optical element 13 as described above, in the case inwhich a higher extinction ratio (contrast) is required, it is desirableto provide the polarization plate also on the side of the entrance endface 13 a.

Further, although the wire grid polarization plate is used as thepolarization plate 15, the polarization plate 15 is not limited thereto.For example, although the polarization plate 15 made of inorganicmaterials is used, a polarization plate made of organic materials canalso be used.

Further, although such a polarization plate as to reflect the componentnot conforming to the transmission axis is adopted, such a polarizationplate as to absorb the component not conforming to the transmission axiscan also be adopted.

Further, although as the laser beam to be input to the optical element13, the laser beam vibrating in an arranging direction of the intensitymodulating electrodes 11 a, 11 b is used, the direction is not limitedthereto. Further, it is possible to use a polarization plate having atransmission axis corresponding to the polarization direction of thelaser beam entering the optical element 13 as the polarization plate 15.

Further, although the modulating area T1 and the scanning area T2 areseparately provided in one optical element 13, an electro-optic element20 having the modulating area T1 and the scanning area T2 overlappingeach other can also be adopted. Specifically, as shown in FIG. 4, theelectro-optic element 20 is provided with intensity modulatingelectrodes 21 a, 21 b respectively on the one surface 13 c and the othersurface 13 d of the optical element 13 opposed to each other, and withscanning electrodes 22 a, 22 b respectively on surfaces 13 e, 13 fopposed to each other in a direction perpendicular to the one surface 13c of the optical element 13. Thus, the intensity modulation and thescanning of the incident laser beam can be performed in the same area.

In the present configuration, since the modulating area T1 and thescanning area T2 are realized in the same area to reduce the elementlength of the optical element 13, it becomes possible to achievedownsizing and cost reduction. Further, since the emission time of thelaser beam from entrance to emission in the optical element 13 isshortened by reducing the element length of the optical element 13, thescanning speed of the light beam emitted from the optical element 13 canbe increased.

Further, although each of the intensity modulating electrode 11 a andthe scanning electrode 12 a is disposed in the area obtained by dividingthe optical element 13 into two substantially equal parts, but this isnot a limitation.

Further, although the electro-optic element 1 scans the laser beam onlyin one direction, bi-directional scanning in which the incident lightbeam to the optical element 13 is scanned towards the both sidescentering around the incident light beam can also be adopted.

Second Embodiment

A second embodiment according to the invention will now be explainedwith reference to FIG. 5.

In the present embodiment, an image display device (scanning opticaldevice) 30 equipped with the electro-optic element 1 of the firstembodiment described above as a scanning device will be explained.

It should be noted that in the embodiments described hereinafter,portions having configurations common to the electro-optic element 1according to the first embodiment will be denoted with the samereference numerals, and the explanations therefor will be omitted.

As shown in FIG. 5, the image display device 30 according to the presentembodiment is provided with a red light source device (a light sourcedevice) 30R for emitting red laser beam with a center wavelength of 630nm, a green light source device (a light source device) 30G for emittinggreen laser beam with a center wavelength of 530 nm, a blue light sourcedevice (a light source device) 30B for emitting blue laser beam with acenter wavelength of 450 nm, a cross dichroic prism 31, theelectro-optic element 1 for scanning the laser beam emitted from thecross dichroic prism (a color composition section) 31 in a horizontaldirection of a screen (an irradiated surface) 35, a galvanometer mirror32 for scanning the laser beam emitted from the electro-optic element 1in a vertical direction of the screen 35, and the screen 35 on which thelaser beam scanned by the galvanometer mirror 32 is projected.

Further, the green light source 30G is formed of a Diode Pumped SolidState (DPSS) laser including a semiconductor laser (LD) and a wavelengthconversion element, wherein the laser beam emitted by the semiconductorlaser is converted into the green laser beam with a center wavelength of530 nm by the wavelength conversion element.

A polarization plate (a polarization selection member) 36 used in thepresent embodiment functions on the light beam in the wavelength rangeof the green laser beam, namely the wavelength range of 490 nm through570 nm. Specifically, the polarization plate 36 has a configuration oftransmitting a polarized light beam with a specific polarizationdirection out of the green laser beam, and reflecting a polarized lightbeam with a polarization direction substantially perpendicular to thespecific polarization direction. Thus, since the polarization plate 36does not function on the light beam outside the wavelength range of 490nm through 570 nm, the red laser beam and the blue laser beam aretransmitted without being modulated.

A method of projecting an image on the screen 35 using the image displaydevice 30 according to the present embodiment thus configured will nowbe explained.

The laser beams emitted from the light source devices 30R, 30G, and 30Bare combined by the cross dichroic prism 31, and enter the electro-opticelement 1. All of the polarization planes of the colored light beams,namely the red, green, and blue laser beams, entering the opticalelement 13 are rotated in the modulating area T1 in accordance with avoltage applied between the intensity modulating electrodes 11 a, 11 b.Further, the light beam entering from the modulating area T1 to thescanning area T2 is scanned in the horizontal direction of the screen35, and scanned in the vertical direction thereof by the galvanometermirror 32, thus projected on the screen 35.

On this occasion, all of the polarization plane of the colored lightbeams, namely the red, green, and blue laser beams are rotated bytransmitted through the modulating area T1, and when transmitted throughthe polarization plate 36 of the electro-optic element 1, a componentnot conforming to the polarization direction of the polarization plate36 is reflected while the light beam with a component conforming to thepolarization direction is transmitted through the polarization plate 36to be emitted therefrom with respect only to the green laser beam. Inthis way, the intensity modulation of the green laser beam entering theoptical element 13 is performed.

Further, regarding the red and blue laser beams, the intensitymodulation is performed by controlling the current or the voltageapplied to the light source devices 30R, 30B.

In the image display device 30 according to the present embodiment,since the wavelength conversion element is used in the green lightsource device 30G, the modulation rate of the green light source device30G is lower than the modulation rates of the red light source device30R and the blue light source device 30B. However, since thepolarization plate 36 functions on the light beam in the wavelengthrange of the green laser beam, only the green laser beam is modulatedout of the laser beams emitted from the optical element 13. Therefore,by controlling the voltage applied between the intensity modulationelectrodes 11 a, 11 b, the modulation rate of the green laser beam canbe increased. Thus, since the modulation rates of the light sourcedevices 30R, 30G, and 30B for emitting a plurality of laser beams withdifferent wavelengths can be made equal to each other, it is possible toirradiate the same area with the same timing. Therefore, it becomespossible to project a clear image on the screen 35.

Further, in the image display device 30 according to the presentembodiment, since the electro-optic element 1 with a large deflectionangle is used as the scanning device, the display device can correspondto the Super Video Graphics Array (SVGA) class resolution. Therefore, animage can more clearly be displayed on the screen while achieving lowpower consumption without causing deterioration in image quality.

Moreover, since the scanning device formed of the electro-optic element1 can perform scanning faster than the MEMS scanners, by using theelectro-optic scanner for the horizontal scanning and the galvanometermirror 32 (a movable scanning device for reflecting light while moving)for the vertical scanning with a lot of flexibility as in the presentembodiment, it can be expected to realize a high performance imagedisplay device. It should be noted that the scanning can be performed bya polygon mirror, which is moderate in price, and one of movablescanning devices, instead of the galvanometer mirror 32. By using theinexpensive polygon mirror, a high performance image display can beperformed with moderate cost.

Third Embodiment

A third embodiment according to the invention will now be explained withreference to FIGS. 6 through 9.

An image display device 40 according to the present embodiment isdifferent from the image display device of the second embodiment in theconfiguration of the electro-optic element 41.

Specifically, although in the second embodiment, only the modulationrate of the green light source device 30G is controlled, the imagedisplay device 40 of the present third embodiment is provided with anelectro-optic element 41 capable of controlling the modulation of all ofthe red laser beam, green laser beam, and blue laser beam respectivelyemitted from the red light source device 30R, green light source device30G, and blue light source device 30B.

As shown in FIG. 6, the electro-optic element 41 is provided with apolarization plate (a polarization selection member) 45 so as to havecontact with the emission end face 13 b of the optical element 13. Thepolarization plate 45 functions on the light beams in the entirewavelength range including the wavelength range of the red laser beam,the wavelength range of the green laser beam, and the wavelength rangeof the blue laser beam.

As shown in FIG. 7, the electro-optic element 41 is composed of themodulating area T1 and the scanning area T2. Further, as shown in FIG.8, the modulating area T1 is composed of a red modulating area T1R, agreen modulating area T1G, and a blue modulating area T1B obtained bydividing the modulating area T1 into three substantially equal partsalong the width direction of the optical element 13. It should be notedthat the scanning area T2 has the same configuration as in the secondembodiment.

Further, the red modulating area T1R is an area held between a redintensity modulating electrode 42 a provided on the one surface 13 c anda red intensity modulating electrode 42 b provided on the other surface13 d. It is arranged that the red laser beam LR emitted from the redlight source device 30R enters this area T1R. Similarly, the greenmodulating area T1G is an area held between green intensity modulatingelectrodes 43 a, 43 b, and arranged so that the green laser beam LG isinput thereto, and the blue modulating area T1B is an area held betweenblue intensity modulating electrodes 44 a, 44 b, and arranged so thatthe blue laser beam LB is input thereto. The electrode material of allof these intensity modulating electrodes 42 a, 42 b, 43 a, 43 b, 44 a,and 44 b is Pt.

Further, as shown in FIG. 8, a power supply Er is provided between thered intensity modulating electrodes 42 a, 42 b, and similarly, a powersupply Eg is provided between the green intensity modulating electrodes43 a, 43 b, and a power supply Eb is provided between the blue intensitymodulating electrodes 44 a, 44 b. Further, pulse signals with voltagevalues corresponding to the light beam intensities are applied betweenthe electrodes 42 a, 42 b, the electrodes 43 a, 43 b, and the electrodes44 a, 44 b by the power supplies Er, Eg, and Eb, respectively.

Thus, as shown in FIG. 7, the laser beams LR, LG, and LB input to therespective modulating areas T1R, T1G, and T1B enter the scanning area T2with the polarization planes rotated in accordance with the voltagevalues of the pulse signals, respectively. Further, by applying avoltage between the scanning electrodes 12 a, 12 b by the power supplyE2 in the scanning area T2, the red, green, and blue laser beams LR, LG,and LB entering the scanning area T2 from the respective modulatingareas T1R, T1G, and T1B are deflected towards the scanning electrode 12b influenced by the same electric field inside the optical element 13.Further, the red, green, and blue laser beams LR, LG, and LB thusdeflected in the scanning area T2 are transmitted through thepolarization plate 45 in accordance with the polarization planes of therespective laser beams, and emitted therefrom.

FIG. 9 shows the red, green, and blue laser beams LR, LG, and LB scannedon the screen 35.

As shown in FIG. 9, the red, green, and blue laser beams emitted fromthe electro-optic element 41 simultaneously form three scanning linesrespectively corresponding to the blue laser beam LB, the green laserbeam LG, and the red laser beam LR sequentially from the upper end 35 ato the lower end 35 b of the screen 35. On this occasion, in the firsthorizontal scanning, since the blue laser beam LB and the green laserbeam LG scan above (outside the screen 35) the upper end 35 a of thescreen 35, the blue light source device 30B and the green light sourcedevice 30G are kept out. Then, the green light source device 30G is puton from, for example, the second horizontal scanning, and the blue lightsource device 30B is put on from, for example, the third horizontalscanning.

Further, since the red laser beam LR scans below (outside the screen 35)the lower end 35 b of the screen 35 from, for example, the second lasthorizontal scanning, the red light source device 30R is put out, andsince the green laser beam LG scans below (outside the screen 35) thelower end 35 b of the screen 35 in the last horizontal scanning, thegreen light source device 30G is put out.

In the image display device 40 according to the present embodiment,since the red, green, and blue laser beams respectively emitted from thered, green, and blue light source devices 30R, 30G, and 30B are input tothe red, green, and blue modulating areas T1R, T1G, and T1B differentfrom each other of the optical element 13, it becomes possible tomodulate the laser beams separately from each other. Thus, bycontrolling the voltages applied between the intensity modulatingelectrodes 42 a, 42 b, between the intensity modulating electrodes 43 a,43 b, and between the intensity modulating electrodes 44 a, 44 b,respectively, the amount of modulation can be varied for each of thelaser beams. Therefore, even in the case in which the modulation ratesof the laser beams emitted from the red, green, and blue light sourcedevices 30R, 30G, and 30B are not sufficient for the appropriatedisplay, a sufficiently high modulation rate can be obtained for each ofthe light beams in one element, and further, the modulations differentfrom each other can be executed on the respective light beams.Therefore, it becomes possible to project a clear image on the screen35.

Fourth Embodiment

A fourth embodiment according to the invention will now be explainedwith reference to FIGS. 10 and 11.

In the image display device 40 of the third embodiment, the laser beamsare input to the respective areas in order for controlling themodulation rates of all of the red, green, and blue laser beams. Animage display device 50 according to the present fourth embodiment isdifferent from the image display device 40 according to the thirdembodiment in that the red, green, and blue laser beams are input to thesame modulating area T1 to control the modulation rates of the red,green, and blue laser beams. Further, as the electro-optic element, theelectro-optic element 1 used in the first embodiment is used. It shouldbe noted that the polarization plate 15 provided to the emission endface 13 b of the electro-optic element 1 functions on the light beams inthe entire wavelength range including the wavelength range of the redlaser beam, the wavelength range of the green laser beam, and thewavelength range of the blue laser beam.

As shown in FIG. 10, the image display device 50 is provided with acontrol section 51 for controlling driving of the red, green, and bluelight source devices 30R, 30G, and 30B.

The control section 51 performs the color sequential drive on the redlight source device 30R, the green light source device 30G, and the bluelight source device 30B in this order so that the red laser beam, thegreen laser beam, and the blue laser beam are sequentially emitted inevery frame (a period of time for drawing one color image) as shown in atiming chart of FIG. 11.

In the case in which a frame of three-color image is drawn with the red,green, and blue laser beams in a time period of tF, a drawing period ofeach laser beam every frame makes tF/3. Further, since each laser beamis modulated in the modulating area T1, only the ON/OFF control isrequired for each of the light source devices 30R, 30G, and 30B.

Firstly, the red light source device 30R is made operate by the controlsection 51, and one frame of image is drawn with the red laser beamemitted from the red light source device 30R. Specifically, the redlaser beam is rotated to have a predetermined polarization plane in themodulating area T1, and then input to the scanning area T2 to bedeflected towards the scanning electrode 12 b. Then, the laser beamdeflected in the scanning area T2 is transmitted through thepolarization plate 15 in accordance with the polarization plane, andthen emitted therefrom. Further, during a period when the drawing by thered light source device 30R proceeds, the control section 51 controlsthe green light source device 30G and the blue light source device 30Bto keep an OFF state.

After the drawing has been performed by the red light source device 30R,the green light source device 30G is made operate by the control section51, and the drawing of the one frame of image with the green laser beamis performed similarly to the case with the red laser beam. Further,during a period when the drawing by the green light source device 30Gproceeds, the control section 51 controls the red light source device30R and the blue light source device 30B to keep an OFF state.

Then, after the drawing has been performed by the green light sourcedevice 30G, the blue light source device 30B is made operate by thecontrol section 51, and the drawing of the one frame of image with theblue laser beam is performed similarly to the case with the red laserbeam. Further, during a period when the drawing by the blue light sourcedevice 30B proceeds, the control section 51 controls the red lightsource device 30R and the green light source device 30G to keep an OFFstate.

As described above, the one frame of image of each of the colored lightbeams is formed with each of the red, green, and blue laser beams, and afull-color image is formed by overlapping these images on a human eye.

Further, as shown in FIG. 11, the voltage waveform to be applied to thescanning electrodes 12 a, 12 b is the same as the waveform shown in FIG.3. Further, as shown in FIG. 11, the voltage signal corresponding to thelight intensity is applied to the intensity modulating electrodes 11 a,11 b.

In the image display device 50 according to the present embodiment,since the red, green, and blue laser beams are scanned in atime-sequential manner in the drawing period for one frame by thecontrol section 51, these laser beams can be input to the samemodulating area T1 of the optical element 13. Therefore, since theintensity modulating electrodes provided for each of the laser beamswith different wavelengths as in the image display device 40 accordingto the third embodiment are not required, downsizing and moderatemanufacturing cost can be achieved.

Further, since the laser beams with different wavelengths are scannedevery frame, each laser beam is irradiated for a longer period of timecompared to the case of scanning the laser beams every line, the drivingcontrol of the light source devices 30R, 30G, and 30B by the controlsection 51 becomes simple. Further, since the color shift caused by adrawing method does not occur, a clear image can be projected on thescreen 35.

Fifth Embodiment

A fifth embodiment according to the invention will now be explained withreference to FIGS. 10 and 12.

In the image display device 50 according to the fourth embodimentdescribed above, the control section 51 controls the light sourcedevices 30R, 30G, and 30B to scan the red, green, and blue laser beamsevery frame. In the image display device 60 according to the fifthembodiment, the control section 61 controls the light source devices30R, 30G, and 30B so as to scan the red, green, and blue laser beamsevery line (a line in the horizontal direction composing a color image).

It should be noted that the schematic overall configuration diagram ofthe image display device 60 of the present embodiment is the same asthat of the image display device 50 according to the fourth embodiment.

As shown in FIG. 10, the image display device 60 is provided with acontrol section 61 for controlling driving of the red, green, and bluelight source devices 30R, 30G, and 30B.

The control section 61 performs the color sequential drive on the redlight source device 30R, the green light source device 30G, and the bluelight source device 30B in this order so that the red laser beam, thegreen laser beam, and the blue laser beam are sequentially emitted inevery line as shown in a timing chart of FIG. 12.

In the case in which a line of three-color image is drawn with the red,green, and blue laser beams in a time period of tL, a drawing period ofeach laser beam every one line makes tL/3. Since each laser beam ismodulated in the modulating area T1, only the ON/OFF control is requiredfor each of the light source devices 30R, 30G, and 30B.

Firstly, the red light source device 30R is made operate by the controlsection 61, and one line of image is drawn with the red laser beamemitted from the red light source device 30R. Specifically, the redlaser beam is rotated to have a predetermined polarization plane in themodulating area T1, and then input to the scanning area T2 to bedeflected towards the scanning electrode 12 b. Then, the laser beamdeflected in the scanning area T2 is transmitted through thepolarization plate 15 in accordance with the polarization plane, andthen emitted therefrom. Further, during a period when the drawing by thered light source device 30R proceeds, the control section 61 controlsthe green light source device 30G and the blue light source device 30Bto keep an OFF state.

After the drawing has been performed by the red light source device 30R,the green light source device 30G is made operate by the control section61, and the drawing of the one line of image with the green laser beamis performed similarly to the case with the red laser beam. Further,during a period when the drawing by the green light source device 30Gproceeds, the control section 61 controls the red light source device30R and the blue light source device 30B to keep an OFF state.

Then, after the drawing has been performed by the green light sourcedevice 30G, the blue light source device 30B is made operate by thecontrol section 61, and the drawing of the one line of image with theblue laser beam is performed similarly to the case with the red laserbeam. Further, during a period when the drawing by the blue light sourcedevice 30B proceeds, the control section 61 controls the red lightsource device 30R and the green light source device 30G to keep an OFFstate.

As described above, an appropriate display is obtained by overlappingthe red, green, and blue laser beams every line on a human eye.

In the image display device 60 according to the present embodiment, thesame advantage as in the image display device 50 according to the fourthembodiment can be obtained. Further, in the image display device 60according to the present embodiment, since the red, green, and bluelaser beams are scanned in a time sequential manner in a drawing periodfor one line so as to be overlapped with each other every line, therepeating frequency of the color becomes higher compared to the case ofscanning the laser beams with different wavelengths every frame, thusoccurrence of the color break-up can be suppressed. Further, since thedriving speed of the galvanometer mirror 32, namely the verticalscanning rate of the screen 35, can be lowered compared to the case ofscanning the laser beams with different wavelengths every frame, theslow galvanometer mirror 32 can also be adopted, thus cost reduction ispossible.

It should be noted that the scope of the present invention is notlimited to the embodiments described above, but various modificationscan be executed thereon within the range of the scope or the spirit ofthe invention.

For example, although in each of the embodiments described above, theexplanations have been made exemplifying the KTN crystal as the opticalelement, the optical element is not limited thereto, but can be anyelements with refractive indexes varying linearly. For example, theoptical element can be a dielectric crystal having an electro-opticeffect such as lithium niobate (LiNbO₃). However, since the crystalhaving a component such as LiNbO₃ has a smaller scanning deflectionangle and a higher drive voltage compared to the KTN crystal, it ispreferable to use the KTN crystal.

Further, although as the colored light composition section, the crossdichroic prism is used, the colored light composition section is notlimited thereto. As the colored light composition section, what hasdichroic mirrors in a cross arrangement to combine the colored lightbeams, or what has dichroic mirrors arranged in parallel to each otherto combine the colored light beams can be used.

The entire disclosure of Japanese Patent Application No. 2007-045120,filed Feb. 26, 2007 is expressly incorporated by reference herein.

1. An electro-optic element comprising: an electro-optic crystal havinga birefringent property, and in which a refractive index distribution isgenerated in accordance with an intensity of an electric field causedinside; a pair of intensity modulating electrodes formed of a materialincapable of having an ohmic contact with the electro-optic crystal; apair of scanning electrodes formed of a material capable of having anohmic contact with the electro-optic crystal; and a polarizationselection member provided at least on a side of a laser beam emissionend face out of a laser beam entrance end face and the laser beamemission end face of the electro-optic crystal, and for selectivelytransmitting a part with a specific vibration direction out of a lightbeam emitted from the electro-optic crystal; wherein the electro-opticcrystal comprising a modulating area between the intensity modulatingelectrodes and a scanning area between the scanning electrodes, themodulating area and the scanning area being sequentially disposed fromthe laser beam entrance end face along a proceeding direction of thelaser beam with the modulating area being near the entrance end face. 2.The electro-optic element according to claim 1, wherein the material ofthe intensity modulating electrodes is Pt.
 3. The electro-optic elementaccording to claim 1, wherein the material of the intensity modulatingelectrodes has a Schottky barrier.
 4. The electro-optic elementaccording to claim 1, wherein the material of the scanning electrodes isTi.
 5. The electro-optic element according to claim 1, wherein theelectro-optic crystal includes a component of KTa_(1-x)Nb_(x)O₃.
 6. Ascanning optical device comprising: a light source device for emitting alaser beam; and the electro-optic element according to claim 1 whichmodulates the laser beam emitted from the light source device inaccordance with an image signal, and scans the laser beam towards anirradiated surface.
 7. The scanning optical device according to claim 6,wherein the light source device emits a plurality of laser beams withwavelengths different from each other, and the polarization selectionmember selectively transmits a part with a specific vibration directionout of the laser beam in a specific wavelength range out of wavelengthranges of the plurality of laser beams, and transmits the laser beamsoutside the specific wavelength range irrespective of vibrationdirections.
 8. The scanning optical device according to claim 6, whereinthe light source device emits a plurality of laser beams withwavelengths different from each other, the plurality of laser beams isrespectively input to different areas of the electro-optic crystal, andthe pair of intensity modulating electrodes is separately provided toeach of the different areas.
 9. The scanning optical device according toclaim 6, wherein the light source device emits a plurality of laserbeams with wavelengths different from each other, and there is provideda control section for controlling driving of the light source device sothat the plurality of laser beams is scanned in a time sequential mannerin a drawing period for one frame.
 10. The scanning optical deviceaccording to claim 6, wherein the light source device emits a pluralityof laser beams with wavelengths different from each other, and there isprovided a control section for controlling driving of the light sourcedevice so that the plurality of laser beams is scanned in a timesequential manner in a drawing period for one line.
 11. The scanningoptical device according to claim 6, wherein the electro-optic elementperforms horizontal scanning.